In external floating roof storage tanks, the floating roof is adapted to float on the product stored in the tank. It is known to provide monitoring systems for floating tank roofs.
The purpose with this type of system is to have control of the floating roof, i.e. to make sure that dangerous situations related to cases when the roof does not float properly on the product surface are detected. There are also advantages related to environmental requirements, e.g. to avoid evaporation of volatile hydrocarbons into the environment in case the roof gets flooded with product. Finally, the monitoring system may eliminate or at least reduce the need for inspection activities. Typically the pontoons of a floating roof must be inspected for leakage every year or even every quarter by a person that opens up the hatches in the pontoons. This type of work has certain personal risks and could be minimized with the roof tilt system.
The monitored distance between the floating roof and the product surface is normally substantially constant. Due to external influence such as wind, rain or snow, minor deviations of a few cm are acceptable, but deviations exceeding a certain threshold (e.g. more than 5 cm in some applications) typically indicate some kind of fault or undesired condition.
It would be desirable to provide diagnostics functionality for predicting when there are prevailing fault conditions, so that such fault conditions may be addressed before any incident occurs.